Touch sensor

ABSTRACT

A touch sensor includes a substrate, sensing channels, and a protective layer. The sensing channels are disposed at intervals on a surface of the substrate, and any one of the sensing channels includes an electrode portion and a silver trace portion electrically connected to the electrode portion. The protective layer is disposed on the substrate and covers and encapsulates the sensing channels. After the touch sensor is subjected to a salt spray test with sodium chloride solution of a mass percentage concentration of 5% at a rate of 1 mL/H to 2 mL/H under an ambient temperature of 35° C. for 48 hours, a resistance change rate of any one of the sensing channels is less than or equal to 10%, and a resistance distribution difference between the sensing channels is less than or equal to 10%.

BACKGROUND Field of Disclosure

The present disclosure relates to a touch sensor.

Description of Related Art

For metal materials, the salt spray corrosion is a common anddestructive atmospheric corrosion. Chloride ions in the salt spray canpenetrate the oxide layer on the surface of the metal material andelectrochemically react with the internal metal of the metal material,resulting in defects in the metal material. Therefore, many electronicproducts are often subjected to a salt spray test to detect theircorrosion resistance to the salt spray.

In general, whether an electronic product has passed the salt spray testis usually judged by a naked-eye inspection of the appearance of theelectronic product. For example, for a touch sensor, it is usuallythrough a naked-eye inspection to determine whether the metal componentssuch as electrodes and circuits have traces, discoloration, and otherchanges on the surfaces of the metal components. However, under therequirements of higher quality standards to the electronic product, thetraditional naked-eye inspection is unable to accurately determinewhether the salt spray test has caused damage to the metal components,which often leads to the distortion of the inspection results and thedeterioration of product quality. Therefore, how to provide a touchsensor that can provide a normal operation function after the salt spraytest is currently worth studying.

SUMMARY

According to some embodiments of the present disclosure, a touch sensorincludes a substrate, a plurality of sensing channels, and a protectivelayer. The sensing channels are disposed at intervals on a surface ofthe substrate, and any one of the sensing channels includes an electrodeportion and a silver trace portion electrically connected to theelectrode portion. The protective layer is disposed on the substrate andcovers and encapsulates the sensing channels. After the touch sensor issubjected to a salt spray test with sodium chloride solution of a masspercentage concentration of 5% at a rate of 1 mL/H to 2 mL/H under anambient temperature of 35° C. for 48 hours, a resistance change rate ofany one of the sensing channels is less than or equal to 10%, and aresistance distribution difference between the sensing channels is lessthan or equal to 10%.

In some embodiments of the present disclosure, the protective layerdirectly contacts a carrying surface of the substrate and a top surfaceof the silver trace portion, the protective layer has an upper surfacefacing away from the substrate, and a vertical distance between theupper surface of the protective layer and the top surface of the silvertrace portion is greater than or equal to 20% of a thickness of thesilver trace portion.

In some embodiments of the present disclosure, a sum of the verticaldistance between the upper surface of the protective layer and the topsurface of the silver trace portion and a vertical distance between thetop surface of the silver trace portion and the carrying surface of thesubstrate is less than or equal to 12 μm.

In some embodiments of the present disclosure, a thickness of the silvertrace portion is greater than or equal to 1 μm and less than or equal to9 μm.

In some embodiments of the present disclosure, a water vaporpermeability of the protective layer is greater than or equal to 400g/(m²×day) and less than or equal to 1500 g/(m²×day).

In some embodiments of the present disclosure, the electrode portion isa metal nanowire electrode portion including a matrix and a plurality ofmetal nanowires distributed in the matrix.

In some embodiments of the present disclosure, at least any one of thesensing channels further includes a metal nanowire trace portion. Themetal nanowire trace portion and the silver trace portion are disposedin a stack, the metal nanowire trace portion is between the silver traceportion and the substrate, the metal nanowire trace portion is connectedto the metal nanowire electrode portion, the metal nanowire traceportion and the metal nanowire electrode portion are on a samehorizontal plane, and the metal nanowire trace portion and the silvertrace portion at least constitute a peripheral circuit of the touchsensor.

In some embodiments of the present disclosure, the protective layerdirectly contacts a carrying surface of the substrate and a top surfaceof the silver trace portion, the protective layer has an upper surfacefacing away from the substrate, a vertical distance between the uppersurface of the protective layer and the top surface of the silver traceportion is greater than or equal to 20% of a thickness of the silvertrace portion, and a sum of the vertical distance between the uppersurface of the protective layer and the top surface of the silver traceportion and a vertical distance between the top surface of the silvertrace portion and the carrying surface of the substrate is less than orequal to 12 μm.

In some embodiments of the present disclosure, the electrode portion hasa mesh pattern, and the electrode portion and the silver trace portionare on a same horizontal plane.

In some embodiments of the present disclosure, the electrode portion atleast constitutes a touch electrode of the touch sensor, and the silvertrace portion at least constitutes a peripheral circuit of the touchsensor.

According to the aforementioned embodiments of the present disclosure,after the touch sensor of the present disclosure is subjected to thesalt spray test for 48 hours, the resistance change rate of any one ofsensing channels of the touch sensor is low, and the resistancedistribution difference between the sensing channels is low, having theelectrical specifications defined by the present disclosure.Accordingly, when inspected by the electrical test which is morerigorous and accurate compared to the appearance inspection, the touchsensor of the present disclosure can be ensured to provide a normaloperation function after the salt spray test.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be more fully understood by reading the followingdetailed description of the embodiments, with reference made to theaccompanying drawings as follows:

FIG. 1 is a schematic partial cross-sectional view illustrating a touchsensor according to some embodiments of the present disclosure;

FIG. 2 is a schematic view illustrating a measurement method ofresistance of the sensing channels according to some embodiments of thepresent disclosure;

FIG. 3 is a schematic partial cross-sectional view illustrating a touchsensor according to some other embodiments of the present disclosure;and

FIG. 4 is a scanning electron microscope (SEM) image of a touch sensorafter being subjected to a salt spray test.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments of thedisclosure, examples of which are illustrated in the accompanyingdrawings. However, it should be understood that these details should notbe intend to limit the present disclosure. In addition, for theconvenience of readers, the size of each element in the drawings is notillustrated according to actual scale. It should be understood thatrelative terms such as “lower” or “bottom” and “upper” or “top” can beused herein to describe the relationship between one element and anotherelement, as shown in the figures. It should be understood that relativeterms are intended to include different orientations of the device otherthan those shown in the figures.

Reference is made to FIG. 1 , which is a schematic partialcross-sectional view illustrating a touch sensor 100 according to someembodiments of the present disclosure. The touch sensor 100 includes asubstrate 110, a plurality of sensing channels 120 (only a portion ofone of the sensing channels 120 is shown in FIG. 1 ), and a protectivelayer 130. In some embodiments, the touch sensor 100 has a visible areaVA and a peripheral area PA, and the peripheral area PA is at leastdisposed on one side of the visible area VA. The substrate 110 isconfigured to carry the sensing channels 120 and the protective layer130, and may be, for example, a rigid transparent substrate or aflexible transparent substrate. In some embodiments, a material of thesubstrate 110 includes, but is not limited to, transparent materialssuch as glass, acrylic, polyvinyl chloride, polypropylene, polystyrene,polycarbonate, cycloolefin polymer, cycloolefin copolymer, polyethyleneterephthalate, polyethylene naphthalate, colorless polyimide, orcombinations thereof. In some embodiments, the substrate 110 may besurface-treated or be coated with coating layers (not shown) withdifferent functional requirements (e.g., optical and reliabilityrequirements). In the present disclosure, these additionalsurface-treated layers or coating layers are regarded as a portion ofthe substrate 110.

The sensing channels 120 are disposed on the carrying surface 111 of thesubstrate 110 at intervals, and a single sensing channel 120 extendsfrom the visible area VA to the peripheral area PA to form an electrontransferring path across the visible area VA and the peripheral area PA.Specifically, a single sensing channel 120 includes an electrode portion120 a and a silver trace portion 120 b, in which the electrode portion120 a is located in the visible area VA and partially extends into theperipheral area PA so as to achieve a touch function, and the silvertrace portion 120 b is located in the periphery area PA and electricallyconnected to the electrode portion 120 a so as to transmit signals to anelectronic component such as an external controller. In other words, theelectrode portion 120 a can at least constitute a touch electrode of thetouch sensor 100, and the silver trace portion 120 b can at leastconstitute a peripheral circuit of the touch sensor 100. In theembodiment shown in FIG. 1 , the electrical connection between theelectrode portion 120 a and the silver trace portion 120 b is achievedby covering a portion of the silver trace portion 120 b with theelectrode portion 120 a which extends into the peripheral area PA. Thatis, the electrode portion 120 a and the silver trace portion 120 b areoverlapped with each other in the peripheral area PA of the touch sensor100 to be electrically connected to each other.

The electrode portion 120 a can have a variety of configurations, and avariety of materials can be chosen as the material of the electrodeportion 120 a, such that the touch sensor 100 can provide diverse andwide applications. In some embodiments, the electrode portion 120 a maybe a single-sided single-layer, double-sided single-layer, single-sideddouble-layer, or bridge-type single-layer electrode structure disposedon the substrate 110. In the embodiment shown in FIG. 1 , the electrodeportion 120 a is an example of a single-layer electrode structuredisposed on a single surface (side) of the substrate 110, in which aplurality of the electrode portion 120 a are arranged in anon-interlaced manner. For example, the electrode portions 120 a may bestrip-shaped electrodes extending along a first direction D1 andarranged at intervals along a second direction D2, in which the firstdirection D1 is perpendicular to the second direction D2. In someembodiments, the electrode portion 120 a may be, for example, a metalnanowire electrode portion, a metal electrode portion, or a metal oxideelectrode portion. Specifically, the metal nanowire electrode portionmay include a matrix and a plurality of metal nanowires distributed inthe matrix, in which the matrix may include polymers such aspolyacrylate, epoxy resin, polysiloxane, polysilane, poly(silicon-acrylic acid), polyurethane, or mixtures thereof, and the metalnanowires may include silver nanowires, gold nanowires, coppernanowires, nickel nanowires, or combinations thereof. Specifically, themetal electrode portion may include silver metal or copper metal, andwhen the electrode portion 120 a is the metal electrode portion, theelectrode portion 120 a may further be designed to have a specialpattern, such as a mesh pattern formed by a plurality of interlaced thinmetal lines, such that visibility of the electrode portion 120 a isreduced. In addition, the electrode portion 120 a and the silver traceportion 120 b are on a same horizontal plane (i.e., the electrodeportion 120 a is coplanar with the silver trace portion 120 b, which isnot shown in the drawings). Specifically, the metal oxide electrodeportion may include indium tin oxide, indium zinc oxide, cadmium tinoxide, aluminum-doped zinc oxide, or combinations thereof. In thefollowing embodiments, the electrode portion 120 a is exemplified by themetal nanowire electrode portion.

The silver trace portion 120 b includes silver metal. The silver traceportion 120 b can be formed on the carrying surface 111 of the substrate110 and on at least a portion of the electrode portion 120 a extendinginto the peripheral area PA by screen printing, and the silver traceportion 120 b has a top surface 121 b (i.e., a surface of the silvertrace portion 120 b (facing) away from the substrate 110) after beingformed. Specifically, solution including silver paste may be formed onthe substrate 110 by screen printing, and then the solution may becured/dried, such that a silver layer is formed all over the peripheralarea PA. Then, the silver layer is patterned, such that the silver traceportion 120 b is formed in the peripheral area PA.

The protective layer 130 is disposed on an entire surface of thesubstrate 110, and the coverage of the protective layer 130 includes thevisible area VA and the peripheral area PA, so as to cover each of thesensing channels 120 on the substrate 110. That is, the protective layer130 covers each of the electrode portions 120 a and each of the silvertrace portions 120 b. In some embodiments, the material of theprotective layer 130 can be an insulating material such as acrylicmaterial, fluorine-including acrylic material, epoxy resin, orcombinations thereof, in which the acrylic material can be, for example,poly(methylmethacrylate) (PMMA). The protective layer 130 can protectthe sensing channels 120 from being corroded by water vapor, such thatthe electrical specifications of the touch sensor 100 of the presentdisclosure at least meet the relationships of Equation (1) and Equation(2) after being subjected to a salt spray test with sodium chloridesolution of a mass percentage concentration of 5% and a PH value of 6.5to 7.2 at a rate of 1 mL/H to 2 mL/H for 48 hours (for the operationmethod of the salt spray test, please refer to the standard methodGB/T2423.17:2008 “Environmental Testing of Electrical and ElectronicProducts, Part II: Test method Ka: salt spray”). Equation (1) andEquation (2) are reproduced below:(R _(T48) −R _(T0))/R _(T0)≤10%,  Equation (1):(R _(MAX) −R _(MIN))/(R _(MAX) +R _(MIN))≤10%.  Equation (2):

In Equation (1), R_(T0) is the resistance of any one of the sensingchannels 120 of the touch sensor 100 before the salt spray test, andR_(T48) is the resistance of the same sensing channel 120 after 48 hoursof the salt spray test. In other words, Equation (1) represents thatafter the touch sensor 100 is subjected to the salt spray test for 48hours, the resistance change rate of any one of the sensing channels 120is less than or equal to 10%. In Equation (2), R_(MAX) is the resistanceof the sensing channel 120 with the largest resistance among all of thesensing channels 120 after 48 hours of the salt spray test, and R_(MIN)is the resistance of the sensing channel 120 with the smallestresistance among all of the sensing channels 120 after 48 hours of thesalt spray test. In other words, Equation (2) represents that after thetouch sensor 100 is subjected to the salt spray test for 48 hours, theresistance distribution difference between all of the sensing channels120 is less than or equal to 10%. It should be understood that “theresistance distribution difference between the sensing channels 120” inthe present disclosure refers to “the degree of the resistancedifference between the sensing channels 120”. When the resistancedistribution difference between the sensing channels 120 is smaller, theresistance distribution range of all of the sensing channels 120 issmaller, and the resistance of all of the sensing channels 120 iscloser. Based on satisfying the above electrical specifications, thetouch sensor 100 of the present disclosure. Based on satisfying theabove electrical specifications, the touch sensor 100 provided by thepresent disclosure can provide a normal touch operation function afterthe salt spray test regardless of whether there are traces ordiscoloration on the appearance of the top surface 121 b of the silvertrace portion 120 b.

A method for measuring resistance of the sensing channels 120 is furthersupplemented. Reference is made to FIG. 2 , which is a schematic viewillustrating a measurement method of resistance of the sensing channels120. In the measurement method, the measurement equipment is Flukemultimeter (model: F287C) with a first probe and a second probe, and themeasurement is carried out under a normal temperature environment.Specifically, the measurement method includes the following steps. Step1: Turn on the power of the measurement equipment, and set theequipment's rotary switch to resistance measurement position. Step 2:Bring the two probes into contact with each other to calibrate forzeroing. Step 3: Placing the calibrated first probe to contact anyposition P1 of an end of an electrode portion 120 a of a sensing channel120, and placing the calibrated second probe after to contact anyposition P2 of an end of a silver trace portion 120 b of the samesensing channel 120 which is usually designed as a conductive pad 150,such that the resistance of the sensing channel 120 is measured. Step 4:repeating Step 3 for three times, calculating an average value of thethree resistance obtained by the three measurements, and regarding theaverage value as the resistance of the sensing channel 120. After theabove steps, the resistance R_(T0) in Equation (1) can be obtained.Next, after the touch sensor 100 is subjected to the salt spray testunder the aforementioned conditions for 48 hours, the touch sensor 100is removed from the salt spray test environment, and then Step 1 to Step4 are sequentially carried out on the same sensing channel 120 of whichthe resistance R_(T0) has been measured, such that the resistanceR_(T48) in Equation (1) can be obtained. In addition, after the touchsensor 100 subjected to the salt spray test under the aforementionedconditions for 48 hours, the touch sensor 100 is removed from the saltspray test environment, and then Step 1 to Step 4 are sequentiallycarried out on all of the sensing channels 120, such that the resistanceR_(MAX) and R_(MIN) in Equation (2) can be obtained.

In some embodiments, the electrical specifications of the touch sensor100 may further satisfy the condition of “the insulation resistancebetween two adjacent sensing channels 120 of the sensing channels 120 isgreater than or equal to 100 MO” to ensure that no short circuit occursbetween adjacent sensing channels 120. The method for measuring theinsulation resistance may include the following steps. Firstly, theaforementioned Step 1 and Step 2 are sequentially performed. Next, afterStep 2 is performed, the calibrated first probe is placed to contact anyposition P3 of any of the touch sensing channels 120, and then thecalibrated second probe is placed to contact any position P4 of asensing channel 120 adjacent to the sensing channel 120 that is incontact with the calibrated first probe. Accordingly, the insulationresistance between the two adjacent sensing channels 120 is obtained.

A special design between the protective layer 130 and the silver traceportion 120 b of the touch sensor 100 is further discussed in thefollowing. The protective layer 130 directly contacts the carryingsurface 111 of the substrate 110 and the top surface 121 b of the silvertrace portion 120 b, and the protective layer 130 has an upper surface131 facing away from the substrate 110. Through the design of therelationship between a vertical distance d2 between the top surface 131of the protective layer 130 and the top surface 121 b of the silvertrace portion 120 b (i.e., a thickness T2 of the protective layer 130directly above the silver trace portion 120 b) and a vertical distanced1 between the top surface 121 b of the silver trace portion 120 b andthe carrying surface 111 of the substrate 110 (i.e., a thickness T1 ofthe silver trace portion 120 b), and through the design of the materialproperties of the protective layer 130, the touch sensor 100 of thepresent disclosure can be ensured to pass the electrical test which ismore rigorous and accurate compared to the appearance inspection afterbeing subjected to the salt spray test for 48 hours. In the followingdescription, “the relationship between the thickness T2 of theprotective layer 130 and the thickness T1 of the silver trace portion120 b” and “the material properties of the protective layer 130” will besequentially discussed.

Regarding the design of “the relationship between the thickness T2 ofthe protective layer 130 and the thickness T1 of the silver traceportion 120 b”, in general, when the thickness T2 of the protectivelayer 130 covering the top of the silver trace portion 120 b is larger,the protection of the protective layer 130 for the silver trace portion120 b is stronger. That is, when the thickness T2 of the protectivelayer 130 increases, the protective layer 130 gives a positive impact onthe probability of the touch sensor 100 passing the electrical testafter the salt spray test. However, if the thickness T2 of theprotective layer 130 is too large, the optical properties of the touchsensor 100 may be adversely affected, the bendability of the touchsensor 100 may be limited, and the cost may be increased. Aftercomprehensively considering the above factors, the thickness T2 of theprotective layer 130 and the thickness T1 of the silver trace portion120 b of the present disclosure are designed to meet the relationshipsof Equation (3) and Equation (4) reproduce below:T2≥T1×20%,  Equation (3):T1+T2≤12 μm.  Equation (4):

In Equation (3) and Equation (4), T1 is the thickness of the silvertrace portion 120 b, and T2 is the thickness of the protective layer 130covering from the top of the silver trace portion 120 b. In other words,Equation (3) represents that the thickness T2 of the protective layer130 covering from the top of the silver trace portion 120 b is greaterthan or equal to 20% of the thickness T1 of the silver trace portion 120b. That is, the vertical distance d2 between the upper surface 131 ofthe protective layer 130 and the top surface 121 b of the silver traceportion 120 b is greater than or equal to 20% of the thickness T1 of thesilver trace portion 120 b. In addition, Equation (4) represents a sumof the thickness T1 of the silver trace portion 120 b and the thicknessT2 of the protective layer 130 covering from the top of the silver traceportion 120 b is less than or equal to 12 μm. That is, a sum of thevertical distance d2 between the upper surface 131 of the protectivelayer 130 and the top surface 121 b of the silver trace portion 120 band the vertical distance d1 between the top surface 121 b of the silvertrace portion 120 b and the carrying surface 111 of the substrate 110 isless than or equal to 12 μm. Since the thickness T2 of the protectivelayer 130 and the thickness T1 of the silver trace portion 120 b meetthe relationships of Equation (3) and Equation (4), the touch sensor 100can meet the electrical, reliability, optical, and structural (e.g.,bendability) requirements of the touch sensor 100.

In some embodiments, the protective layer 130 can be formed on thesubstrate 110 by screen printing. Based on the limit of the totalthickness of the protective layer 130 that can be formed by a singlescreen-printing process, the sum of the thickness T1 of the silver traceportion 120 b and the thickness T2 of the protective layer 130 coveringthe silver trace portion 120 b is controlled to be less than or equal to12 μm in the present disclosure. As such, the touch sensor 100 can meetthe electrical, reliability, optical, and structural (e.g., bendability)requirements of the touch sensor 100 under the premise of onlyperforming the screen-printing process once to form the protective layer130 and taking into account the cost considerations. For example, aninsulating material with a thickness of about 6 μm to 8 μm can be formedon the silver trace portion 120 b by a single screen-printing process,and the insulating material that is not fully cured (i.e., not fullyshaped) may partially flow into the intervals between the adjacentsilver trace portions 120 b. Accordingly, the sum of the thickness T2 ofthe protective layer 130 cured and covering the silver trace portion 120b and the thickness T1 of the silver trace portion 120 b (i.e., thethickness T1+thickness T2) is controlled to be less than or equal to 12μm. In other words, in order to meet the requirements of the electricalproperties and reliability of the touch sensor 100, if the sum of thethickness T1 and the thickness T2 is designed to be greater than 12 μm,multiple screen-printing processes will be performed, which may lead toan increase in cost and an increase in the overall thickness of thetouch sensor 100, resulting in failure to meet the aforementionedrequirements of the present disclosure. As a supplementary note, aperson having ordinary skill in the art can understand that the factorsaffecting the thickness of a layer formed by screen printing mayinclude, for example, parameters such as squeegee speed ofscreen-printing, screen mesh count, squeegee pressure ofscreen-printing, etc.

As another supplementary note, during the screen-printing process of thesilver trace portion 120 b, the silver paste may be picked up by thescreen-printing plate while removing the screen-printing plate,resulting in a slight uneven and undulating appearance on the topsurface 121 b of the silver trace portion 120 b formed. Therefore, whenviewed on a microscopic scale, the top surface 121 b of the silver traceportion 120 b is usually a non-planar surface as shown in the partiallyenlarged region in FIG. 1 . In the present disclosure, a degree ofuniformity of the top surface 121 b of the silver trace portion 120 bcan be further quantified through the “uniform percentage, expressed bythe symbol U (%), of which the unit is %”. More specifically, theuniform percentage of the top surface 121 b of the silver trace portion120 b can be defined by Equation (5) reproduced below:U(%)=[(D _(MAX) −D _(MIN))/(D _(MAX) +D _(MIN))]  Equation (5):

In Equation (5), D_(MAX) is a vertical distance between the carryingsurface 111 of the substrate 110 and the highest point A of the topsurface 121 b of one selected silver trace portion 120 b, in which thehighest point A is selected among 4 points randomly selected on the topsurface 121 b of the selected silver trace portion 120 b when observingfrom the optical microscope within the observation range of 10 times theobjective lens and 10 times the eye lens; D_(MIN) is a vertical distancebetween the carrying surface 111 of the substrate 110 and the lowestpoint B of the top surface 121 b of the selected silver trace portion120 b among the above selected 4 points. When the degree of uniformityof the top surface 121 b of the silver trace portion 120 b is quantifiedby Equation (5), it is preferable to control the uniformity distributionto be greater than or equal to 10% and less than or equal to 30%. Whenthe uniformity distribution is larger, the height difference betweeneach point on the top surface 121 b of the silver trace portion 120 b islarger (i.e., the degree of fluctuation is larger), and the top surface121 b of the silver trace portion 120 b is more uneven and undulating.Since the uniformity distribution of the top surface 121 b of the silvertrace portion 120 b is controlled within the above-mentioned suitablerange, the additional influence made by the uniformity distribution ofthe top surface 121 b of the silver trace portion 120 b on the design ofthe relationships between the thickness T2 of the protective layer 130and the thickness T1 of the silver trace portion 120 b can be furtherreduced.

In addition, since the silver trace portion 120 b may be formed byscreen printing, the viscosity of the silver paste may affect thethickness T1 of the silver trace portion 120 b, and may also affect thedegree of uniformity (uniformity distribution) of the top surface 121 bof the silver trace portion 120 b. In general, when the viscosity of thesilver paste is higher, the thickness T1 of the silver trace portion 120b formed by screen printing can be larger, and the trace resistance ofthe silver trace portion 120 b can be smaller. However, when theviscosity of the silver paste is higher, the controllability of screenprinting for the silver paste may be worse, resulting in a worse (ahigher) uniformity distribution of the top surface 121 b of the silvertrace portion 120 b. The viscosity of the silver paste used in thepresent disclosure may be greater than or equal to 1000 cp and less thanor equal to 100000 cp. When the viscosity of the silver paste is 1000cp, the thickness T1 of the silver trace portion 120 b that can beimplemented is greater than or equal to 1 μm and less than or equal to 2μm, and the uniformity distribution of the top surface 121 b of thesilver trace portion 120 b can be controlled to be about 10%; when theviscosity of the silver paste is 100000 cp, the thickness T1 of thesilver trace portion 120 b that can be implemented is greater than orequal to 6 μm and less than or equal to 9 μm, and the uniformitydistribution of the top surface 121 b of the silver trace portion 120 bcan be controlled to be about 30%. In other words, in consideration ofreliability and electrical properties, the thickness T1 of the silvertrace portion 120 b of the present disclosure is preferably designed tobe greater than or equal to 1 μm and less than or equal to 9 μm, suchthat the uniformity distribution of the top surface 121 b of the silvertrace portion 120 b can be greater than or equal to 10% and less than orequal to 30%. Accordingly, the silver trace portion 120 b can meet theelectrical transmission requirements, and the additional influence madeby the uniformity distribution of the top surface 121 b of the silvertrace portion 120 b on the design of the relationships between thethickness T2 of the protective layer 130 and the thickness T1 of thesilver trace portion 120 b can be further reduced, in which therelationships between the thickness T2 of the protective layer 130 andthe thickness T1 of the silver trace portion 120 b are designed to meetthe reliability requirements.

The above supplementary note to the uniformity distribution is mainlyfor explaining that the deviation caused by the uniformity distributionof the top surface 121 b of the silver line portion 120 b is implied inthe thicknesses T1 and T2 in Equation (3) and Equation (4) of thepresent disclosure. In addition, since the thickness T1 of the silvertrace portion 120 b is generally much larger than the thickness T4 ofthe electrode portion 120 a (the thickness T1 of the silver traceportion 120 b is generally about 100 times the thickness T4 of theelectrode portion 120 a), the thickness T4 of the electrode portion 120a is negligible at the overlapping position of the silver trace portion120 b and the electrode portion 120 a. That is, the thickness T4 of theelectrode portion 120 a does not affect the interpretation of therelationships of Equation (3) and Equation (4). In more detail, at theoverlapping position of the silver trace portion 120 b and the electrodeportion 120 a, the thickness T1 of the silver trace portion 120 b can beregarded as the vertical distance d1 between the top surface 121 b ofthe silver trace portion 120 b and the carrying surface 111 of thesubstrate 110.

Regarding the design of “the material properties of the protective layer130”, the water vapor permeability of the protective layer 130 mayaffect the water blocking ability of the protective layer 130, whichfurther affects the protection of the protective layer 130 to the silvertrace portion 120 b. In general, when the water vapor permeability ofthe protective layer 130 is lower, the water blocking ability of theprotective layer 130 is stronger, and the protection that can beprovided for the silver trace portion 120 b is stronger. However, whenthe water vapor permeability of the protective layer 130 is lower, thedegree of curing of the protective layer 130 is higher, the hardness ofthe protective layer 130 is greater, the bending property of theprotective layer 130 is poorer, and the protective layer 130 is moreexpensive, which are not conducive to reducing costs. Aftercomprehensively considering the above factors, the water vaporpermeability of the protective layer 130 of the present disclosure isdesigned to be greater than or equal to 400 g/(m²×day) and less than orequal to 1500 g/(m²×day). As such, during the salt spray test, theprotective layer 130 is not only designed in terms of structure (e.g.,the relationships of thickness), but also material properties to providebetter protection, such that the silver trace portion 120 b can beprotected from water vapor erosion, the bendability of the touch sensor100 can be taken into consideration, and the costs can be reduced. Inaddition, when the electrode portion 120 a of the touch sensor 100 ofthe present embodiment is, for example, the metal nanowire electrodeportion as described above, the protective layer 130 having theabove-mentioned water vapor permeability can further effectively preventthe metal nanowires in the metal nanowire electrode portion frominfluence made by water vapor. That is, the protective layer 130 canavoid constructing an environment that facilitates ion migration,thereby avoiding ion migration of the metal nanowires in the electrodeportion 120 a or slowing down the ion migration rate of the metalnanowires and helping to improve the reliability of the touch sensor100.

Reference is made to FIG. 3 , which is a schematic partialcross-sectional view illustrating a touch sensor 100 a according to someother embodiments of the present disclosure. At least one differencebetween the embodiment of FIG. 3 and the embodiment of FIG. 1 is thatthe sensing channel 120 of the touch sensor 100 a in FIG. 3 furtherincludes a metal nanowire trace portion 120 c stacked with the silvertrace portion 120 b, in which the metal nanowire trace portion 120 c isdisposed between the silver trace portion 120 b and the substrate 110,and the metal nanowire trace portion 120 c contacts the silver traceportion 120 b. The metal nanowire trace portion 120 c includes a matrixand a plurality of metal nanowires distributed in the matrix. In someembodiments, when the electrode portion 120 a is the metal nanowireelectrode portion 120 a, the metal nanowire trace portion 120 c and themetal nanowire electrode portion 120 a are connected to each other andare integrally formed on a same horizontal plane (i.e., the metalnanowire trace portion 120 c and the metal nanowire electrode portion120 a are coplanar). In addition, the metal nanowire trace portion 120 cand the silver trace portion 120 b may at least constitute a peripheralcircuit of the touch sensor 100. Based on the above, by integrallyforming the metal nanowire electrode portion 120 a and the metalnanowire trace portion 120 c to directly form an electrical connection(i.e., by making the metal nanowire electrode portion 120 a and themetal nanowire trace portion 120 c belong to different portions of asingle-layer metal nanowire layer), there is no need for an additionalcontact structure for realizing the electrical contact between theperipheral circuit and the touch electrode, such that an area occupiedby the contact structure in the peripheral area PA can be saved.

It is worth noting that since the thickness T5 of the metal nanowiretrace portion 120 c is the same as the thickness T4 of the metalnanowire electrode portion 120 a (i.e., the thickness T1 of the silvertrace portion 120 b is also much larger than the thickness T5 of themetal nanowire trace portion 120 c), for the embodiment shown in FIG. 3, when calculating the relationships of the aforementioned Equation (3)and Equation (4), the thickness T5 of the metal nanowire trace portion120 c and the thickness T4 of the metal nanowire electrode portion 120 aare both negligible. In other words, the thickness T1 of the silvertrace portion 120 b can be regarded as the vertical distance d1 betweenthe top surface 121 b of the silver trace portion 120 b and the carryingsurface 111 of the substrate 110.

Hereinafter, the features and effects of the present disclosure will beverified in more detail with reference to the touch sensors of eachembodiment and each comparative example. Reference is made to Table 1,which lists the electrical properties of touch sensors with the silvertrace portions 120 b with different thicknesses T1 and the protectivelayers 130 with different thicknesses T2 after being subjected to thesalt spray test for 48 hours. In Table 1, the stack structure of eachtouch sensor is the same as the stack structure shown in FIG. 1 . In theembodiments/comparative examples, the silver trace portions 120 b withthe thicknesses T1 of 1 μm and 2 μm were made of the silver paste with aviscosity of 1000 cp, the silver trace portions 120 b with thethicknesses T1 of 3 μm and 4.5 μm were made of the silver paste with aviscosity of 30000 cp, the silver trace portions 120 b with thethicknesses T1 of 6 μm, 7.5 μm, and 9 μm were made of the silver pastewith a viscosity of 100000 cp, and the protective layer 130 was made ofPMMA with a water vapor permeability of 1230 g/(m²×day). In addition,the electrical test results shown in Table 1 are obtained through theaforementioned resistance measurement method, and when the electricaltest result is expressed as “pass”, it means that the electricalperformance (electrical specifications) of the touch sensor at least metthe relationships of the aforementioned Equation (1) and Equation (2),and when the electrical test result is expressed as “fail”, it meansthat the electrical performance of the touch sensor at least did notmeet one of the aforementioned Equation (1) and Equation (2). It shouldbe understood that without exceeding the scope of the presentdisclosure, the touch sensor in Table 1 should not be used to limit thepresent disclosure.

TABLE 1 Electrical Properties Thickness T2 of Protective Layers Coveringof Touch Sensors Silver Trace Portions (μm) after Salt Spray Test 0.51.0 1.5 2 2.5 3.0 Thickness 1.0 Pass Pass Pass Pass Pass Pass T1 ofSilver 2.0 Trace (μm) 3.0 Fail 4.5 6.0 Fail 7.5 9.0 Fail

It can be seen from the electrical results in Table 1 that when thethickness T2 of the protective layer 130 covering the silver traceportion 120 b is greater than or equal to 20% of the thickness T1 of thesilver trace portion 120 b, and the sum of the thickness T1 of thesilver trace portion 120 b and the thickness T2 of the protective layer130 covering the silver trace portion 120 b is less than or equal to 12μm (i.e., when the thickness T2 of the protective layer 130 and thethickness T1 of the silver trace portion 120 b meet the relationships ofthe aforementioned Equation (3) and Equation (4)), the touch sensor canpass the electrical specifications defined in the present disclosurethrough electrical measurement after the salt spray test. From this, itcan be seen that the design of the relationships between the thicknessT2 of the protective layer 130 and the thickness T1 of the silver traceportion 120 b of the present disclosure can ensure that the touch sensor100 still provide a normal operation function after the salt spray test,which effectively improves the reliability of touch sensor.

On the other hand, FIG. 4 is a scanning electron microscope (SEM) imageof a touch sensor after being subjected to a salt spray test when thethickness T1 of the silver trace portion 120 b and the thickness T2 ofthe protective layer 130 in Table 1 did not meet the relationship ofEquation (3). More specifically, in the touch sensor of FIG. 4 , thethickness T1 of the silver trace portion 120 b is 7.1 μm, and thethickness T2 of the protective layer 130 is 1.1 μm. It is worth notingthat under the scale of the scanning electron microscope, it can be seenthat although the protective layer 130 was not pierced and damaged bythe silver trace portion 120 b, and the silver trace portion 120 b wasnot exposed by the protective layer 130, but the silver trace portion120 b had actually been defective. From this, it can be seen that in theart, it is impossible to accurately judge whether the protective layer130 and the silver trace portion 120 b have changed and the specificdegree of change after the salt spray test by naked-eye inspections. Inparticular, since the silver trace portion 120 b is covered by theprotective layer 130, it is more difficult to judge whether the silvertrace portion 120 b have changed and the specific degree of change afterthe salt spray test from the appearance of the silver trace portion 120b. Therefore, it can be proved that one cannot effectively judge whetherthe structure of the touch sensor is still complete after the salt spraytest and whether the touch sensor provides the function that meets theelectrical specifications after the salt spray test by simply observingthe appearance of the touch sensor.

According to the aforementioned embodiments of the present disclosure,since in the touch sensor of the present disclosure, there is a specialrelationship between the thickness of the protective layer and thethickness of the silver trace portion, and the material properties(e.g., the water vapor permeability) of the protective layer are alsoproperly adjusted and screened, it is helpful to improve the protectionof the protective layer to the silver trace portion, and avoid theproblems of structural defects and electrical failure caused by thewater vapor erosion of the silver trace portion. The present disclosureconducts electrical tests on the touch sensor after the salt spray test.The test results show that after the touch sensor of the presentdisclosure is subjected to the salt spray test, the resistance changerate of any one of the sensing channels is low, and the resistancedistribution difference between the sensing channels is low, having theelectrical specifications defined by the present disclosure. From this,it can be seen that when inspected by the electrical test which is morerigorous and accurate compared to the appearance inspection, the touchsensor of the present disclosure can be ensured to provide a normaloperation function after the salt spray test.

Although the present disclosure has been described in considerabledetail with reference to certain embodiments thereof, other embodimentsare possible. Therefore, the spirit and scope of the appended claimsshould not be limited to the description of the embodiments containedherein.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentdisclosure without departing from the scope or spirit of the disclosure.In view of the foregoing, it is intended that the present disclosurecovers modifications and variations of this disclosure provided theyfall within the scope of the following claims.

What is claimed is:
 1. A touch sensor, comprising: a substrate; aplurality of sensing channels disposed at intervals on a surface of thesubstrate, wherein each of the sensing channels comprises: an electrodeportion; and a silver trace portion electrically connected to theelectrode portion; and a protective layer disposed on the substrate andcovering and encapsulating the sensing channels; wherein the sensingchannels and the protective layer are configured to withstand a saltspray test, and, after the touch sensor is subjected to the salt spraytest with sodium chloride solution of a mass percentage concentration of5% at a rate of 1 mL/H to 2 mL/H under an ambient temperature of 35° C.for 48 hours, a resistance change rate of any one of the sensingchannels is less than or equal to 10%, and a resistance distributiondifference between the sensing channels is less than or equal to 10%. 2.The touch sensor of claim 1, wherein the protective layer directlycontacts a carrying surface of the substrate and a top surface of thesilver trace portion, the protective layer has an upper surface facingaway from the substrate, and a vertical distance between the uppersurface of the protective layer and the top surface of the silver traceportion is greater than or equal to 20% of a thickness of the silvertrace portion.
 3. The touch sensor of claim 2, wherein a sum of thevertical distance between the upper surface of the protective layer andthe top surface of the silver trace portion and a vertical distancebetween the top surface of the silver trace portion and the carryingsurface of the substrate is less than or equal to 12 μm.
 4. The touchsensor of claim 2, wherein a thickness of the silver trace portion isgreater than or equal to 1 μm and less than or equal to 9 μm.
 5. Thetouch sensor of claim 1, wherein a water vapor permeability of theprotective layer is greater than or equal to 400 g/(m²×day), grams persquare meter per day, and less than or equal to 1500 g/(m²×day).
 6. Thetouch sensor of claim 1, wherein the electrode portion is a metalnanowire electrode portion comprising a matrix and a plurality of metalnanowires distributed in the matrix.
 7. The touch sensor of claim 6,wherein at least any one of the sensing channels further comprises: ametal nanowire trace portion, wherein the metal nanowire trace portionand the silver trace portion are disposed in a stack, the metal nanowiretrace portion is between the silver trace portion and the substrate, themetal nanowire trace portion is connected to the metal nanowireelectrode portion, the metal nanowire trace portion and the metalnanowire electrode portion are on a same horizontal plane, and the metalnanowire trace portion and the silver trace portion at least constitutea peripheral circuit of the touch sensor.
 8. The touch sensor of claim7, wherein the protective layer directly contacts a carrying surface ofthe substrate and a top surface of the silver trace portion, theprotective layer has an upper surface facing away from the substrate, avertical distance between the upper surface of the protective layer andthe top surface of the silver trace portion is greater than or equal to20% of a thickness of the silver trace portion, and a sum of thevertical distance between the upper surface of the protective layer andthe top surface of the silver trace portion and a vertical distancebetween the top surface of the silver trace portion and the carryingsurface of the substrate is less than or equal to 12 μm.
 9. The touchsensor of claim 1, wherein the electrode portion has a mesh pattern, andthe electrode portion and the silver trace portion are on a samehorizontal plane.
 10. The touch sensor of claim 1, wherein the electrodeportion at least constitutes a touch electrode of the touch sensor, andthe silver trace portion at least constitutes a peripheral circuit ofthe touch sensor.
 11. A touch sensor, comprising: a substrate; aplurality of sensing channels disposed at intervals on a surface of thesubstrate; and a protective layer disposed on the substrate and coveringand encapsulating the sensing channels, wherein each of the sensingchannels comprises an electrode portion and a silver trace portionelectrically connected to the electrode portion, wherein the protectivelayer directly contacts a carrying surface of the substrate and a topsurface of the silver trace portion, and the protective layer has anupper surface facing away from the substrate, and a vertical distancebetween the upper surface of the protective layer and the top surface ofthe silver trace portion is greater than or equal to 20% of a thicknessof the silver trace portion, and a sum of the vertical distance betweenthe upper surface of the protective layer and the top surface of thesilver trace portion and a vertical distance between the top surface ofthe silver trace portion and the carrying surface of the substrate isless than or equal to 12 μm; wherein the sensing channels and theprotective layer are configured to withstand a salt spray test, and,after the touch sensor is subjected to the salt spray test with sodiumchloride solution of a mass percentage concentration of 5% at a rate of1 mL/H to 2 mL/H under an ambient temperature of 35° C. for 48 hours, aresistance change rate of any one of the sensing channels is less thanor equal to 10%, and a resistance distribution difference between thesensing channels is less than or equal to 10%.
 12. A touch sensor,comprising: a substrate; a plurality of sensing channels disposed atintervals on a surface of the substrate; and a protective layer disposedon the substrate and covering and encapsulating the sensing channels,wherein each of the sensing channels comprises an electrode portion anda silver trace portion electrically connected to the electrode portion,wherein a water vapor permeability of the protective layer is greaterthan or equal to 400 g/(m²×day) grams per square meter per day, and lessthan or equal to 1500 g/(m²×day), wherein the protective layer directlycontacts a carrying surface of the substrate and a top surface of thesilver trace portion, the protective layer has an upper surface facingaway from the substrate, and a vertical distance between the uppersurface of the protective layer and the top surface of the silver traceportion is greater than or equal to 20% of a thickness of the silvertrace portion; wherein the sensing channels and the protective laver areconfigured to withstand a salt spray test and, after the touch sensor issubjected to the salt spray test with sodium chloride solution of a masspercentage concentration of 5% at a rate of 1 mL/H to 2 mL/H under anambient temperature of 35° C. for 48 hours, a resistance change rate ofany one of the sensing channels is less than or equal to 10%, and aresistance distribution difference between the sensing channels is lessthan or equal to 10%.